The Atlantic Ocean is the second largest of the world's oceanic divisions, following the Pacific Ocean. With a total area of about 106,400,000 square kilometres (41,100,000 sq mi),[1] it covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. The first part of its name refers to Atlas of Greek mythology, making the Atlantic the "Sea of Atlas".

The oldest known mention of "Atlantic" is in The Histories of Herodotus around 450 BC (Hdt. 1.202.4): Atlantis thalassa (Greek: Ἀτλαντὶς θάλασσα; English: Sea of Atlas). The term Ethiopic Ocean, derived from Ethiopia, was applied to the southern Atlantic as late as the mid-19th century.[2] Before Europeans discovered other oceans, their term "ocean" was synonymous with the waters beyond the Strait of Gibraltar that are now known as the Atlantic. The early Greeks believed this ocean to be a gigantic river encircling the world.

The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. As one component of the interconnected global ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica). The equator subdivides it into the North Atlantic Ocean and South Atlantic Ocean. The term "Central Atlantic" refers to the area between South America and Africa north of the Equator;[3] while geographically part of the North Atlantic, its character is very different to the waters to the north between North America and Europe.

In the southeast, the Atlantic merges into the Indian Ocean. The 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. Some authorities show it extending south to Antarctica, while others show it bounded at the 60° parallel by the Southern Ocean.[4]

Covering approximately 22% of Earth's surface, the Atlantic is second in size to the Pacific. With its adjacent seas, it occupies an area of about 106,400,000 square kilometres (41,100,000 sq mi);[1] without them, it has an area of 82,400,000 square kilometres (31,800,000 sq mi). The land that drains into the Atlantic covers four times that of either the Pacific or Indian oceans. The volume of the Atlantic with its adjacent seas is 354,700,000 cubic kilometers (85,100,000 cu mi) and without them 323,600,000 cubic kilometres (77,640,000 cu mi).

The average depth of the Atlantic with its adjacent seas, is 3,339 metres (1,826 fathoms; 10,950 ft); without them it is 3,926 metres (2,147 fathoms; 12,880 ft). The greatest depth, Milwaukee Deep with 8,380 metres (4,580 fathoms; 27,500 ft), is in the Puerto Rico Trench. The Atlantic's width varies from 1,538 nautical miles (2,848 km; 1,770 mi) between Brazil and Sierra Leone to over 3,450 nautical miles (6,400 km; 4,000 mi) in the south.

The Atlantic Ocean was named by the ancient Greeks after either Atlas the Titan or the Atlas Mountains named for him;[5][6] both involve the concept of holding up the sky. Transatlantic travel played a major role in the expansion of Western civilization into the Americas. It is the Atlantic that separates the "Old World" from the "New World". In modern times, some idioms refer to the ocean in a humorously diminutive way as the Pond, describing both the geographical and cultural divide between North America and Europe, in particular between the English-speaking nations of both continents. Many British people refer to the United States and Canada as "across the pond", and vice versa.[7]

The "Black Atlantic" refers to the role of this ocean in shaping black people's history, especially through the Atlantic slave trade. Irish migration to the US is meant when the term "The Green Atlantic" is used. The term "Red Atlantic" has been used in reference to the Marxian concept of an Atlantic working class, as well as to the Atlantic experience of indigenous Americans.
[8][9][10]

The principal feature of the bathymetry (bottom topography) is a submarine mountain range called the Mid-Atlantic Ridge.[11] It extends from Iceland in the north to approximately 58° South latitude, reaching a maximum width of about 860 nautical miles (1,590 km; 990 mi). A great rift valley also extends along the ridge over most of its length. The depth of water at the apex of the ridge is less than 2,700 metres (1,500 fathoms; 8,900 ft) in most places, while the bottom of the ridge is three times as deep. Several peaks rise above the water and form islands.[12] The South Atlantic Ocean has an additional submarine ridge, the Walvis Ridge.[13]

The Mid-Atlantic Ridge separates the Atlantic Ocean into two large troughs with depths from 3700–5500 metres (2,000–3,000 fathoms; 12,000–18,000 ft). Transverse ridges running between the continents and the Mid-Atlantic Ridge divide the ocean floor into numerous basins. Some of the larger basins are the Blake, Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic. The largest South Atlantic basins are the Angola, Cape, Argentina, and Brazil basins.

The deep ocean floor is thought to be fairly flat with occasional deeps, abyssal plains, trenches, seamounts, basins, plateaus, canyons, and some guyots. Various shelves along the margins of the continents constitute about 11% of the bottom topography with few deep channels cut across the continental rise.

Ocean floor trenches and seamounts:

Puerto Rico Trench, in the North Atlantic, is the deepest trench at 8,605 metres (4,705 fathoms; 28,230 ft)[14]

Terrigenous deposits with land origins, consisting of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land washed to sea. These materials are found mostly on the continental shelves and are thickest near large river mouths or off desert coasts.

Pelagic deposits, which contain the remains of organisms that sink to the ocean floor, include red clays and Globigerina, pteropod, and siliceous oozes. Covering most of the ocean floor and ranging in thickness from 60–3300 metres (33–1,800 fathoms; 200–11,000 ft) they are thickest in the convergence belts, notably at the Hamilton Ridge and in upwelling zones.

On average, the Atlantic is the saltiest major ocean; surface water salinity in the open ocean ranges from 33 to 37 parts per thousand (3.3 – 3.7%) by mass and varies with latitude and season. Evaporation, precipitation, river inflow and sea ice melting influence surface salinity values. Although the lowest salinity values are just north of the equator (because of heavy tropical rainfall), in general the lowest values are in the high latitudes and along coasts where large rivers enter. Maximum salinity values occur at about 25° north and south, in subtropical regions with low rainfall and high evaporation.

Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar energy, range from below −2 °C (28.4 °F) to over 30 °C (86 °F). Maximum temperatures occur north of the equator, and minimum values are found in the polar regions. In the middle latitudes, the area of maximum temperature variations, values may vary by 7–8 °C (45–46 °F).

The Atlantic Ocean consists of four major water masses. The North and South Atlantic central waters make up the surface. The sub-Antarctic intermediate water extends to depths of 1,000 metres (550 fathoms; 3,300 ft). The North Atlantic Deep Water reaches depths of as much as 4,000 metres (2,200 fathoms; 13,000 ft). The Antarctic Bottom Water occupies ocean basins at depths greater than 4,000 meters.

Within the North Atlantic, ocean currents isolate the Sargasso Sea, a large elongated body of water, with above average salinity. The Sargasso Sea contains large amounts of seaweed and is also the spawning ground for both the European eel and the American eel.

The Coriolis effect circulates North Atlantic water in a clockwise direction, whereas South Atlantic water circulates counter-clockwise. The south tides in the Atlantic Ocean are semi-diurnal; that is, two high tides occur during each 24 lunar hours. In latitudes above 40° North some east-west oscillation occurs.

Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.

Climate is influenced by the temperatures of the surface waters and water currents as well as winds. Because of the ocean's great capacity to store and release heat, maritime climates are more moderate and have less extreme seasonal variations than inland climates. Precipitation can be approximated from coastal weather data and air temperature from water temperatures.

The oceans are the major source of the atmospheric moisture that is obtained through evaporation. Climatic zones vary with latitude; the warmest zones stretch across the Atlantic north of the equator. The coldest zones are in high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents influence climate by transporting warm and cold waters to other regions. The winds that are cooled or warmed when blowing over these currents influence adjacent land areas.

The Gulf Stream and its northern extension towards Europe, the North Atlantic Drift, for example, warms the atmosphere of the British Isles and north-western Europe and influences weather and climate as far south as the northern Mediterranean. The cold water currents contribute to heavy fog off the coast of eastern Canada (the Grand Banks of Newfoundland area) and Africa's north-western coast. In general, winds transport moisture and air over land areas. Hurricanes develop in the southern part of the North Atlantic Ocean. More local particular weather examples could be found in examples such as the Azores High, Benguela Current, and Nor'easter.

Animation showing the separation of Pangaea, which formed the Atlantic Ocean known today

The Atlantic Ocean appears to be the second youngest of the five oceans. It did not exist prior to 130 million years ago, when the continents that formed from the breakup of the ancestral super continent Pangaea were drifting apart. The Atlantic has been extensively explored since the earliest settlements along its shores.

The Vikings, the Portuguese, and the Spaniards were the most famous among early explorers. After Columbus, European exploration rapidly accelerated, and many new trade routes were established.

Ra II, a ship built from papyrus, was successfully sailed across the Atlantic by Thor Heyerdahl proving that it was possible to cross the Atlantic from Africa using such boats in early epochs of history.

Around 980 – 982, Erik the Red discovered Greenland, geographically and geologically a part of the Americas.

Around 1010, Thorfinnr Karlsefni led an attempted Viking settlement in North America with 160 settlers, but was later driven off by the natives. His son Snorri Thorfinnsson was the first American born (somewhere between 1010 and 1013) to European (Icelandic) immigrant parents.

In April 1563, Nicolas Barre and 20 other stranded Huguenots were the first to build a (crude) boat in the Americas and sail across the Atlantic. They sailed from Charlesfort, South Carolina to just off the coast of England where they were rescued by an English ship. Though they resorted to cannibalism, seven men survived the voyage, including Barre.[15][16]

In 1764, William Harrison (the son of John Harrison) sailed aboard HMS Tartar, with the H-4 time piece. The voyage became the basis for the invention of the global system of Longitude.

In 1952, Ann Davison was the first woman to single-handedly sail the Atlantic Ocean.

In 1965, Robert Manry crossed the Atlantic from the U.S. to England non-stop in a 13.5-foot (4.1-meter) sailboat named "Tinkerbell".[20] Several others also crossed the Atlantic in very small sailboats in the 1960s, none of them non-stop, though.

In 1969 and 1970 Thor Heyerdahl launched expeditions to cross the Atlantic in boats built from papyrus. He succeeded in crossing the Atlantic from Morocco to Barbados after a two-month voyage of 6,100 km with Ra II in 1970, thus conclusively proving that boats such as the Ra could have sailed with the Canary Current across the Atlantic in prehistoric times.[21]

In 1980, Gérard d'Aboville was the first man to cross the Atlantic Ocean rowing solo.

The Atlantic has contributed significantly to the development and economy of surrounding countries. Besides major transatlantic transportation and communication routes, the Atlantic offers abundant petroleum deposits in the sedimentary rocks of the continental shelves. The Atlantic hosts the world's richest fishing resources, especially in the waters covering the shelves. The major fish are cod, haddock, hake, herring, and mackerel.

From October to June the surface is usually covered with sea ice in the Labrador Sea, Denmark Strait, and Baltic Sea. A clockwise warm-water gyre occupies the northern Atlantic, and a counter-clockwise warm-water gyre appears in the southern Atlantic. The Mid-Atlantic Ridge, a rugged north-south centerline for the entire Atlantic basin, first discovered by the Challenger Expedition dominates the ocean floor. This was formed by the vulcanism that also formed the ocean floor and the islands rising from it.

Icebergs are common from February to August in the Davis Strait, Denmark Strait, and the northwestern Atlantic and have been spotted as far south as Bermuda and Madeira. Ships are subject to superstructureicing in the extreme north from October to May. Persistent fog can be a maritime hazard from May to September, as can hurricanes north of the equator (May to December).

The United States' southeast coast has a long history of shipwrecks due to its many shoals and reefs. The Virginia and North Carolina coasts were particularly dangerous.

The Bermuda Triangle is popularly believed to be the site of numerous aviation and shipping incidents because of unexplained and supposedly mysterious causes, but Coast Guard records do not support this belief.

Hurricanes are also a natural hazard in the Atlantic, but mainly in the northern part of the ocean, rarely tropical cyclones form in the southern parts. Hurricanes usually form between 1 June and 30 November of every year.

In 2005, there was some concern that warm northern European currents were slowing down.[25]

On 7 June 2006, Florida's wildlife commission voted to take the manatee off the state's endangered species list. Some environmentalists worry that this could erode safeguards for the popular sea creature.

Marine pollution is a generic term for the entry into the ocean of potentially hazardous chemicals or particles. The biggest culprits are rivers and with them many agriculture fertilizer chemicals as well as livestock and human waste. The excess of oxygen-depleting chemicals leads to hypoxia and the creation of a dead zone.[26]

Marine debris, which is also known as marine litter, describes human-created waste floating in a body of water. Oceanic debris tends to accumulate at the center of gyres and coastlines, frequently washing aground where it is known as beach litter.